– C – S Gels: Interpretation of 29 H ‐ Si MAS
The detection of bridging tetrahedra, or
2( Q L), in the silica chains constituting – C – S
gels is controversial. While some authors maintain that 29 H ‐ Si MAS can be used to distinguish between NMR 1 and Q 2
units but not between the silicon environments associated with Q 2 (intermediate position) and Q 2( Q L) (intermediate and bridging position) units, others claim the contrary.
The present article addresses this issue with a report on 29 ‐ Si MAS studies of a number of calcium silicate hydrate gels. The findings showed that nuclear magnetic
resonance can differentiate between NMR 2 and Q 2( Q L) units in highly polymerized – C – S
gels with mean chain lengths ( H MCL) of over 12 and / Ca ratios of <1. At higher Si / Ca ratios, however,
the Si MCL declined, with the concomitant rise in 1 units. Under these conditions, in which it was practically impossible to distinguish between Q 2 and Q 2( Q L),
the presence of a single signal for all 2 units was assumed.
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Document Type: Research Article
Publication date: April 1, 2012